Clonal growth of human megakaryocytic progenitor cells in a micro-agar culture system: simultaneous proliferation of megakaryocytic, granulocytic, and erythroid progenitor cells (CFU-M, CFU-C, BFU-E) and T-lymphocytic colonies (CFU-TL)

Immunocytochemical identification of murine and human megakaryocyte colonies in soft-agar cultures

Murine megakaryocyte (MK) colonies in soft-agar cultures were immunocytochemically stained with platelet antiserum and an immuno-alkaline phosphatase procedure. Subsequently, cytochemical staining for acetylcholinesterase was used to confirm the specificity of the immunolabelling technique. The correlation of numbers of megakaryocyte colonies enumerated by independent observers was excellent. A comparable platelet antiserum directed against human platelet epitopes was utilized to identify human MK colonies in soft-agar cultures of human bone marrow. Using this method, we determined that the frequency of detectable human MK colonies in our agar culture system was maximal between days 10 and 12. The immunocytochemical staining technique we have developed for identification of MK colonies in soft-agar cultures yielded good cellular morphology and produced an intensely specific label against a clear background; it therefore facilitated accurate enumeration of MK colonies. This non-fluorescent method avoids dependence upon a non-permanent marker, and allows the simultaneous enumeration of positive and negative colonies.

Effects of clozapine on hematopoiesis and the cytokine system

Using a bioassay for hematopoietic progenitor cells we looked for mechanisms causing clozapine induced neutropenia and agranulocytosis. Micro-agar-cultures of normal peripheral blood mononuclear cells (MNC) of eight patients currently treated with clozapine and of eight probands not receiving any kind of pharmacological treatment were incubated with increasing concentrations of clozapine (0, 7.5, 15, 30 micrograms/ml). Erythropoiesis and megakaryopoiesis were totally unaffected by clozapine. A biologically relevant suppression of granulopoiesis (CFU-GM) could only be shown in cultures incubated with 30 micrograms/ml clozapine. Cytokine analysis presented a strictly dose-dependent suppression of GM-CSF and neopterin release in all cultures. There was no difference between patients and controls at any clozapine concentration. The data support a possible role for cytokines as one mediator of the agranulocytosis producing effects of clozapine.

Cimetidine induced pancytopenia. Effect on human CFU-MIX colony formation

We describe a 26 year-old male with a pancytopenia possibly due to cimetidine. Using progenitor cell culture techniques we investigated the mechanism of this bone marrow toxicity. Our results show a cimetidine dose-dependent inhibition of normal human CFU-GM colony formation as described by Fitchen and Koeffler in 1980. No differences in growth inhibition were found between the patients' recovery marrow and the controls. Toxicity on normal human CFU-MIX colony formation was, however, far more pronounced. At concentrations as low as 5 micrograms/ml the numbers of CFU-MIX colonies were decreased by almost 20% and more than 30% in cultures of two normal bone marrow samples. A significant decrease in CFU-MIX colony size was measured even at therapeutic levels (0.5 micrograms/ml). No obvious decrease in CFU-GM colony size was noticed at low concentrations. Experiments with T-cell- and monocyte-depleted bone marrow samples gave similar results: a pronounced inhibition of the CFU-MIX colony formation at low concentrations of cimetidine whereas the CFU-GM formation was less affected. It is therefore very unlikely that Accessory cells play part in the cimetidine induced CFU-MIX inhibition. Our results suggest the existence of H2 histamine receptors on human CFU-MIX (= multipotent progenitor cell). Blocking these receptors prevents the multipotent progenitor cell from going into the DNA-synthesis phase of the cell cycle.

Abnormal megakaryopoiesis in patients with myelodysplastic syndromes: analysis of cellular and humoral defects

In 13 patients with myelodysplastic syndrome (MDS) mature and immature erythropoietic (CFU-E, BFU-E), granulopoietic (CFU-GM) and megakaryopoietic (CFU-Meg) colony formation from human bone marrow mononuclear cells was evaluated in a microagar culture system. All but three patients exhibited abnormal CFU-Meg. The defect of CFU-Meg paralleled the reduction of BFU-E, whereas CFU-GM number declined to a lesser extent. Not only the CFU-Meg number, but also the number of megakaryocytes (Mk) per colony was reduced suggesting an additional functional CFU-Meg defect. Megakaryocytic growth factor (Meg-CSF) abnormalities in MDS patients were detected using normal nonadherent T-lymphocyte depleted bone marrow cells as target cells for serum testing. Even for sera from patients with a reduction of platelets and bone marrow megakaryocytes Meg-CSF levels were not increased. No cellular or humoral inhibition could be detected in an MDS patient with a 5q- karyotype, who had an isolated defect of the megakaryocytic cell lineage at presentation. Some patients revealed a spontaneous formation of mixed erythrocytic, granulocytic and megakaryocytic clusters in the presence of fetal calf serum or autologous patient serum, probably representing autonomous proliferation of the malignant clone. In conclusion, both cellular and humoral factors can cause abnormalities of the megakaryocytic cell lineage in MDS patients.

Progressive preleukemia presenting amegakaryocytic thrombocytopenic purpura: association of the 5q- syndrome with a decreased megakaryocytic colony formation and a defective production of Meg-CSF

The authors present a patient with the typical clinical picture of an acquired amegakaryocytic thrombocytopenic purpura. After 16 months of observation, the patient developed acute myelomonocytic leukemia. During the preleukemic phase and after progression to overt leukemia, serial in-vitro analyses of megakaryocytic, granulocytic, erythrocytic and T-lymphocytic colony growth were carried out in a microagar culture system. At presentation, a marked diminution of CFU-M was observed, whereas CFU-E, BFU-E, CFU-C and CFU-TL were in the normal range. The CFU-M number remained at its low level during the whole observation period. The CFU-C number declined steadily during the preleukemic period, while BFU-E, CFU-E and CFU-TL remained constant until January 1985 when the patient developed AML. After progression to overt leukemia, a distinct reduction became evident in all colony-forming cells. Cytogenetic studies performed during the preleukemic phase indicated the presence of a 5q- chromosome. The authors submit evidence here that the patient was not only characterized by defective megakaryocytic colony formation but also by a deficiency of functional megakaryocyte colony-stimulating activity. No humoral or cellular inhibitors of CFU-M colony formation were found. It is concluded that in preleukemia with a 5q- chromosome the megakaryocytic cell lineage may be involved in the process that precedes overt leukemia at an earlier time than cells of granulocytic and erythrocytic lineages. In addition, it is shown here that megakaryocytopoiesis during the preleukemic period can be characterized by two different defects: first, an intrinsic megakaryocytic stem cell defect and, second, a deficiency of functional megakaryocytic colony-stimulating activity.

Cloning of early erythroid and mixed myeloid/erythroid human bone marrow progenitor cells: comparison of different sources of burst-promoting activity (BPA)

The ability of conditioned media from the 5637 cell line and human placenta (HPCM) to stimulate the in vitro growth of human early erythroid and mixed myeloid/erythroid clones was tested and compared to phytohemagglutinin-stimulated leukocyte supernatants (PHA-LCM). Both 5637 supernatant and PHA-LCM were equally effective with a linear dose-response relationship. HPCM at various concentrations did not exhibit burst-promoting activity (BPA). Thus, "pluripoietin"-containing media provide a large-scale source of BPA similar in its biological activity to standard sources used for studying human hematopoiesis in vitro.

Megakaryoblastic micromegakaryocytic crisis in chronic myeloid leukemia

Atypical megakaryoblasts (MKB) or megakaryocytes (MK) are occasionally present in the peripheral blood during the terminal development of chronic myeloid leukemia (CML). We report on a 49-year-old female suffering from Ph1 chromosome-positive CML with typical megakaryoblastic transformation in the peripheral blood and in the bone marrow. The small "blasts" were at the most only slightly larger and were occasionally even smaller than lymphocytes but showed megakaryoblastic or atypical megakaryocytic differentiation. The cytoplasmic cytochemical pattern of the atypical megakaryocytic cells was identical to that of large atypical thrombocytes. Platelet peroxidase was detected upon electron-microscopic (EM) examination. Immunologic characterization disclosed the presence of MK-specific antigens. When cultured in vitro on agar, the blasts transformed spontaneously into large mature MK, exhibiting characteristic cytochemical and immunological patterns. Cytogenetic examination of peripheral blood showed severe abnormalities. The patient did not respond to therapy and died 3 months after manifestation of the blast crisis.

A regulatory role of activated T-lymphocytes on human megakaryocytopoiesis in vitro

Cellular interactions responsible for regulating in vitro megakaryocytopoiesis were studied using a microagar culture system which permits the simultaneous proliferation of human megakaryocytic progenitor cells (CFU-M) and T-lymphocytic colonies (CFU-TL). The proliferation of these colony types depends mainly on two factors: phytohaemagglutinin (PHA) and erythropoietin (EP). The direct addition of increasing PHA concentrations to the liquid overlayer resulted in a parallel increase of CFU-M and CFU-TL. If the T-lymphocytes were removed by an E-rosetting technique a marked diminution of CFU-M and CFU-TL numbers was observed. However, monocyte depletion resulted in a marked augmentation of CFU-M proliferation compared to unfractionated mononuclear cells. In order to confirm that the reduction of CFU-M proliferation observed after T-depletion was primarily mediated by the absence of T-lymphocytes, we have co-cultured different concentrations of previously removed autologous T-lymphocytes with a constant number of T-depleted bone marrow cells. A parallel increase of CFU-TL and CFU-M was found if 0.75 - 7.5 X 10(4) T-lymphocytes were added to the culture. In conclusion, our results indicate that activated T-lymphocytes augment proliferation of human bone marrow CFU-M and that monocytes are less important for the growth of megakaryocytic colonies.

Monoclonal antibodies to human myelomonocyte differentiation antigens in the diagnosis of acute myeloid leukemia

The immunological definition of malignant lymphatic cells has already been routinely applied by many laboratories over a number of years. Today it is clear and undisputed that the phenotypic data obtained in that way are often very useful and supporting. The immunological definition of non-lymphoid leukemias is not yet as far advanced. Additional surface markers for the recognition of poorly differentiated non-lymphoid cells are clearly needed. In this paper ten monoclonal antibodies to myeloid surface antigens are described. It is hoped that they are a useful addition to the presently available relatively small panel of well studied myeloid surface markers which are displayed by immature malignant blast cells.